FREXP(3) Linux Programmer's Manual FREXP(3)
frexp, frexpf, frexpl - convert floating-point number to fractional and integral compo-
double frexp(double x, int *exp);
float frexpf(float x, int *exp);
long double frexpl(long double x, int *exp);
Link with -lm.
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE ||
_POSIX_C_SOURCE >= 200112L;
or cc -std=c99
The frexp() function is used to split the number x into a normalized fraction and an expo-
nent which is stored in exp.
The frexp() function returns the normalized fraction. If the argument x is not zero, the
normalized fraction is x times a power of two, and its absolute value is always in the
range 1/2 (inclusive) to 1 (exclusive), that is, [0.5,1).
If x is zero, then the normalized fraction is zero and zero is stored in exp.
If x is a NaN, a NaN is returned, and the value of *exp is unspecified.
If x is positive infinity (negative infinity), positive infinity (negative infinity) is
returned, and the value of *exp is unspecified.
No errors occur.
Multithreading (see pthreads(7))
The frexp(), frexpf(), and frexpl() functions are thread-safe.
C99, POSIX.1-2001. The variant returning double also conforms to SVr4, 4.3BSD, C89.
The program below produces results such as the following:
$ ./a.out 2560
frexp(2560, &e) = 0.625: 0.625 * 2^12 = 2560
$ ./a.out -4
frexp(-4, &e) = -0.5: -0.5 * 2^3 = -4
main(int argc, char *argv)
double x, r;
x = strtod(argv, NULL);
r = frexp(x, &exp);
printf("frexp(%g, &e) = %g: %g * %d^%d = %g\n",
x, r, r, FLT_RADIX, exp, x);
This page is part of release 3.55 of the Linux man-pages project. A description of the
project, and information about reporting bugs, can be found at